The present invention relates to a vehicle control apparatus and a vehicle control method that are applicable to a vehicle having a first mode, in which gas fuel is supplied to an internal combustion engine to drive the vehicle, and a second mode, in which the vehicle is driven by energy other than gas fuel.
Japanese Laid-Open Patent Publication No. 2000-303909 discloses a gas fuel supply device that includes a supply passage for supplying gas fuel to injectors. The supply passage has a manual on-off valve, a first shutoff valve, and a second shutoff valve. The manual on-off valve is manually opened or closed by the user. The first shutoff valve is arranged upstream of the manual on-off valve. The second shutoff valve is arranged downstream of the manual on-off valve. The shutoff valves are controlled to open and close through control by a control apparatus.
When the manual on-off valve and the shutoff valves are open, gas fuel is supplied to the supply passage from a reservoir tank. Gas fuel is supplied to the injectors through the supply passage.
When a leakage determination process for determining whether gas fuel is leaking from the supply passage is performed, injection of gas fuel from the injectors is inhibited, and the shutoff valves are closed. Then, pressure fluctuation in the section of the supply passage between the closed first and second shutoff valves is monitored. If pressure drop is not detected, it is determined that gas fuel is not leaking to the outside from the section of the supply passage. When a pressure drop is detected in the supply passage section between the first and second shutoff valves, it is determined that gas fuel is leaking to the outside from the supply passage.
Known vehicles that can be driven by an engine using gas fuel include a vehicle that mounts a bi-fuel internal combustion engine, which can be driven not only by gas fuel, but also by liquid fuel. In a vehicle that can be drive by using energy other than gas fuel, it is preferable to quickly switch from the gas fuel-powered vehicle traveling to the driving by the other energy when gas fuel is leaking to the outside from the gas fuel supply passage.
As a method for detecting gas fuel leakage from the gas fuel supply passage in such a vehicle, the leakage determination process disclosed in the above described publication may be used. However, since the described leakage determination process is performed after injection of gas fuel from the injectors is inhibited, the leakage determination process can be performed on limited occasions. Particularly, if gas fuel starts leaking to the outside from the supply passage during the gas fuel-powered vehicle traveling, the detection of the leakage will be delayed. This may cause a delay in switching from the gas fuel-powered vehicle traveling to the vehicle traveling by using the energy other than gas fuel.